Method of fabricating heat exchangers



Dec. 20, 1966 PAULS 3,292,247

4 Sheets-Sheet 1 INVENTOR. THE/PO/V F PAULS Dec. 20, 1966 T. F. PAULS 3,292,247

METHOD OF FABRICATING HEAT EXCHANGERS Original Filed May 27, 1965 4 Sheets-Sheet 2 A 7' TORNEV 1966 T. F. PAULS METHOD OF FABRICATING HEAT EXCHANGERS 4 Sheets-Sheet 3 Original Filed May 27, 1965 INVENTOR. THERON F PAULS BY fi FIG-8 A TTORNE Y Dec. 20, 1966 1' PAULS 3,292,247

METHOD OF FABRICA'IING HEAT EXCHANGERS Original Filed May 27, 1965 4 Sheets-Sheet 4 INVENTOR.

THERONF PAULS A T TORNE Y United States Patent 3,292,247 METHOD OF FABRICATING HEAT EXCHANGERS Theron F. Pauls, Godfrey, lll., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Original application May 27, 1965, Ser. No. 459,197. Divided and this application Sept. 15, 1965, Ser. No.

1 Claim. (Cl. 29-157.?!)

This application is a division of copending application Serial No. 459,197, filed May 27, 1965, which in turn is a continuation-in-part of my copending applicat ion Serial No. 287,240, filed June 12, 1963.

This invention relates generally to a method of fabricating heat exchangers, and more particularly to a method of fabricating heat exchange devices suitable for use as radiators or the like.

A commonly used and eflicient type of heat exchange unit for evaporators, air conditioning, condensers, internal combustion engine cooling radiators, and the like is formed from a plurality of superimposed sheets of metal having internally disposed between the sheets a number of conduits generally in a parallel spaced arrangement extending from a first or intake header to a second or outlet header. One or more of such units may be employed; the conduits or tubes serve to carry a heat exchange medium such as water or other coolant in conductive relationship with another medium such as air or other gas passing between the tubes. This type of construction is typical of automobile radiators where, for example, the heated Water issues from the cooling block of the engine with the aid of a pump, first enters one of the two headers, and then passes through a great number of thinwalled, relatively flat, closely spaced tubes between which cooling air is blown and which extend usually vertically from one to the other of the headers. Condensers are also frequently of this same type of construction.

According to one known method of manufacture as illustnated in US. Patent 2,690,002, this type of heat exchange unit may be readily manufactured to provide a great multiplicity of tubes in a sheet of metal. This method involves the application of a suitable predetermined pattern of weld-inhibiting material between component sheets, pressure welding all adjoining areas except those separated by the weld-inhibiting material, thereby forming a unified composite panel, and inflating along the unwelded areas to erect the tubes integral with the resultant tubed panel. Full advantage heretofore has not been taken of this method inasmuch as the tubes formed are of rather flat or oval shape with the major dimensions lying within or parallel to the panel in which the tubes are formed. In many applications it is desirable that the tubes extend not only longitudinally but also extend perpendicularly out of the panel to a considerable extent so as to place a greater number of the tubes in spaced parallel relationship rather than a lesser number in the same plane. This design adapts the units to fabrication as single pieces of large size, a lesser number of which may then be put together for installations where the external medium passes through perforations in the panel transversely to it rather than passing parallel to the panel along its surfaces.

In accordance with the concepts of this invention a sheet metal panel is formed according to the procedure of the above-mentioned US. Patent 2,690,002, to form the desired tubular passageway system in its embryonic form.

This panel is then slit along a plurality of parallel spacedapart lines extending between two oppositely disposed headers to define the interconnecting tubes. The tube portions lying between adjacent slits are then bent or twisted out of the normal plane of the panel so as to dis- ICC pose the tube portions in substantially perpendicular relationship to the plane of the panel.

A plurality of the resulting panels is then combined to achieve a structure having the desired heat exchange capacity. In order to improve the heat transfer characteristics of the device, secondary heat dissipating fin material is then inserted between the parallel opposing surfaces or rolls of adjacent tubes in a novel manner and secured in place. This construction, while extremely simple to fabricate and assemble, presents apractical and highly efficient heat exchanger adapted to provide a maximum amount of external heat exchange medium flow between the tubes with a minimum amount of turbulence or impediment thereto.

Having thus generally described my invention, it becomes a principal object thereof to provide amethod of fabricating a compact and highly efiicient heat exchange device adapted for transfer of heat between an internal and external heat exchange medium.

Another object of the present invention is to provide a method of fabricating a heat exchange device having a plurality of panels each having a plurality of parallel heat transfer tubes interconnected between a pair of headers for maximum flow of an internal heat transfer medium.

Still another object of the present invention is to provide a method of fabricating a 'heat transfer device having a plurality of panels each having a plurality of heat transfer tubes interconnected between a pair of headers, the tubes being elongate in cross-section with the cross-sectional major dimension of the tube being disposed at substantially right angles to the normal plane of the panel from which the device is fabricated.

Still another object of the present invention is to provide a method of fabricating a heat exchange device having a plurality of panels each having a plurality of heat transfer tubes interconnected between a pair of oppositely disposed headers which are bent or twisted out of the normal plane of the panel from which the device is fabricated so as to provide slots or apertures through which an external heat transfer medium may flow unimpeded over the external surfaces of the heat transfer tubes.

It is still a further object of the present invention to provide a method of fabricating a heat exchange device having a plurality of panels each having a plurality of heat transfer tubes interconnected between a pair of headers and having the major cross-sectional dimension disposed at substantially right angles to the normal plane of the panel from which the device is fabricated to provide elongate apertures in which secondary heat dissipating fin stock material is inserted in heat transfer relationship with the outer walls of the tubes to achieve maximum efiiciency of heat exchange between the internal and external heat transfer mediums.

Yet another object of the present invention is to provide a method of fabricating a heat exchange device of the above character for use as automobile radiators, cooling system condensers and evaporators and the like, which is highly eificient, compact, and economical to manufacture.

Further objects and advantages of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of one embodiment of a panel employed in the completed heat exchange device of this invention;

FIGURE 2 is a composite plan view illustrating a number of steps involved in the fabrication of the device of FIGURE 1;

FIGURE 3 is a sectional view taken on line 33 of FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 illustrating the device in an intermediate stage of fabrication;

FIGURE 5 is a fragmentary view similar to FIGURE 4, but on an enlarged scale, illustrating a further stage in the fabrication of the device;

FIGURE 6 is a fragmentary sectional view on an enlarged scale taken on line 6-6 of FIGURE 1;

FIGURE 7 is a fragmentary sectional View on an enlarged scale taken on line 77 of FIGURE 1;

FIGURE 8 is a partial plan view of the panel of FIG- URE 2 after inflation of the tubes; and

FIGURE 9 is a partial cross-sectional view of a heat exchange device employing a plurality of the panels of FIGURE 1.

Referring now to the drawings and particularly to FIGURE 1, there is seen an illustrative embodiment of a heat exchange device employed in this invention and generally indicated by the reference numeral 10. The initial stage of fabrication of this panel is substantially as set forth in great detail in the above-mentioned US. Patent 2,690,002, and is generally illustrated, in conjunction with other steps in the formation of the heat exchange device 10, in FIGURES 2, 3 and 4.

Referring now to FIGURE 2 it will be seen that the panel 10 is initially formed from a plurality of superposed flat metal sheets 12 and 14. Sheet 12 has applied thereto a pattern of weld-preventing material 16 which is a foreshortened version of the desired pattern of tubular passageways in the finished article. This pattern consists of a pair of parallel bands 18 and 20 which are spaced apart adjacent a pair of opposite edges of the stack of sheets formed by the individual sheets 12 and.

14. Interconnecting the two bands 18 and 20 are a plurality of bands 22 of weld-preventing material which cover the extent of sheet 12 intermediate bands 18 and 20 except for elongated parallel islands 24 which are free of weld-preventing material, and which also extend between the aforementioned bands 18 and 20. It will become apparent that the bands 18 and 20 of weld-preventing material correspond to the headers in the finished article and that the bands 22 correspond to the plurality of interconnecting tubes. In order to provide ingress and egress apertures for a heat transfer medium, the bands 18 and 20 may be extended to an edge of sheet 12 as indicated at 26. It will also be seen that a marginal portion of sheet 12 along opposite sides transverse to the aforementioned opposite sideshas been left free of weld-preventing material 16 forming a peripheral marginal area 28 with the exception of the two strips 26 extending to one of the transverse edges for the ultimate provision of openings adapted for connection to an external source of heat transfer medium.

The stack of component sheets 12 and 14 with weldpreventing material 16 sandwiched therebetween is then temporarily secured together as by clamps, spot welding or the like to prevent relative movement between the sheets 12 and 14. The assembly thus formed is then heated to a required temperature and fed through a pair of pressure rolls which exert sufficient pressure on the stack to firmly weld the sheets 12 and 14 together into a single integrated sheet in the areas not coated with the weld-preventing material 16. Simultaneously with the bonding operation the sheets 12 and 14 undergo a substantial reduction in thickness as well as an elongation in the direction of rolling whereby the foreshortened pattern of weld-preventing material is stretched to a length corresponding to the desired pattern of tubular passageways in the finished article. FIGURE 4 illustrates in cross-section the unified sheet 30 with the unwelded portions 32 at this stage of the fabrication.

Referring again to FIGURE 2, it will be seen that a plurality of slits 34 are formed in the islands 24 free of weld-preventing material, the slits extending almost the full length of these islands. An additional slit 36 is provided in the transverse marginal area free of weld-pre- 42 venting material for a purpose hereinafter to become ap parent. The slits 34 and 36 may be formed during any desirable stage of the fabrication process, either in the individual sheets 12 and 14, or after the sandwich of sheets 12 and 14 and weld-preventing material 16 has been formed and temporarily secured together or still alternatively after the aforementioned hot rolling step. Preferably the last mentioned alternative would be se-.

lected so as to eliminate both the problem of proper.

cation process, the unwelded areas 26 which extend to the transverse edge of the unified sheet 30 are mechanically pried open and a suitable nozzle is inserted therein and connected to an external source of pressure fluid. The

pressure fluid is pumped into the unwelded portions defined by the weld-preventing material 16 to expand the sheets 12 and 14 over these portions and thereby create the desired system of internal fluid passageways. The expansion may be carried out either without external restraint thereby resulting in passageway walls having a substantially rounded configuration, or preferably the expansion may be carried out with the composite sheet 30 inserted between suitable dies or platens, either flat. or. shaped, so as to limit the extent to which the passageway 1 walls can expand outwardly, thus creating a tubular passageway of generally rectangular configuration in crosssection as seen in FIGURE 5. The heat exchange device now consists essentially of the flat unified sheet 30 with an expanded pattern oftubular passageways corresponding to the original pattern of weld-preventing material 16, with the bands 18 and 20 forming the headers 40 y and 42.

Referring again to FIGURE 1, the heat exchange device 10 comprises the integrated sheet 30 of generallyl rectangular configuration, having the parallel spaced:

apart internally disposed headers 40 and 42 and the elon- I gate tubular passageways 38. The headers 40 and 42. terminate adjacent an edge of sheet 30 in inlet and outlet openings 44 and 46 respectively to which conduits 48 and 50 respectively are connected for communication of the: heat exchange device with a source of internal heat transfer medium.

It will be seenfrom FIGURE 1and in greater de- 1 tail in the cross-sectional view of FIGURE 6 andthe.

plan view of FIGURE 8that the tubular passageways 38 have 'been twisted out of the normal plane of sheet 30 so as to dispose the major cross-sectional dimension of tubes 38 at approximately right angles to the normal plane of sheet 30. The disposition of tubes 38 is accomplished :by any desirable means, and is of an extent cover-.

ing substantially all of the length of the slits 34 previously formed in the unified sheet 30. Thus, in the fin ished product, the individual tubes 38 are disposed with opposed parallel outer wall surfaces 52 in spaced apart. relationship, providing relatively wide and elongate slots or apertures 54 through which an external heat transfer.

medium can flow substantially unimpeded. Communica- .tion between the headers 40 and 42 and interconnecting tubes 38 is maintained through the interior of the tubes 38 which traverses the transition portions 56 of tubes 38 1 which lie between the point of connection between the headers 40 and 42 and the remainder of the tubes 38 which are disposed in the aforementioned perpendicular.

relationship. Of course, it is desirable to maintain. these transition portions 56 as short as possible within the limits of the bending characteristic of the metal in order to. pro- 1 vide the maximum length of apertures 54 for unimpeded flow of air and, as will be seen in more detail hereinbelow, to provide the maximum amount of space for secondary heat dissipating fins.

Whatever the sequence of the aforementioned events, when the tubular passageways have been completed and the interconnecting tubes 38 bent to the desired relationship secondary heat dissipating fins 58 formed of closely corrugated or pleated fin stock may be inserted and positioned within the elongate spaces or apertures between the opposing faces 52 and tubes 38, and suitably secured therein by conventional means, such as solder, brazing and the like interposed between the panel and the fin stock. It will be noted from FIGURE 6 that when the tubes 38 are bent, the welded portions of sheets 12 and 14 formerly defined by the islands 24 free of weld-preventing material now constitute oppositely directed flanges 60, thereby leaving the opposing faces 52 of tubes 38 smooth an free of any projecting obstructions. Consequently, it is a relatively simple matter to slip the strips of fin stock 58 into place between adjacent tubes for subsequent unification therewith as explained above. In addition the flanges 60 add structural rigidity to the device and also reinforce the leading edge of the tubes for minimizing damage thereto due to stones or other foreign objects which can strike the frontal area of an automotive radiator. Also the flanges constitute additional heat transfer stock.

In order to secure the outermost rows of fin stock 62 and 64 in place, outer retaining strips 66 and 68 are formed by providing the two outermost slits 36 (FIG- URE 1) beyond the pattern of Weld-preventing material 16. Thus, during the hot rolling process a strip of sheets 12 and 14 is bonded together between the outermost slits 36 and adjacent slits 34 which, when twisted in the same manner as tubes 38, form the outer retaining strips 66 and 68 respectively.

Considering now the manner in which a plurality of the panels 30 are to be combined in the production of a radiator or the like, reference is had to FIGURE 9 of the drawings. As can there be seen, a plurality of the panels 30 are first assembled in face-to-face relationship with the tubes 38 and the elongate spaces or apertures between adjacent tubes 38 in alignment with the corresponding tubes or apertures in adjacent panels. The panels 30 are then secured together in superposed, spacedapart relationship in any desired manner, as by the use of a plurality of spacer tubes 70 between adjacent panels 30. Extending through these spacer tubes 70 and through appropriate apertures in the periphery of the panels 30 is a suitable fastening means 71, which secures the panels 30 together and to a suitable support means 72. Sui-table conduits such as 48, 148, and 248 are then connected to each of the panels 30 in the same manner as the conduits 48 and 50 of the panel of FIGURE 1. The conduits employed may be connected such that the panels 30 are in series flow, or as much cooling capacity as required may be achieved by arranging the panels 30 in parallel flow. The resultin assembly may then be secured in any desired position as by suitable connection to the support means 72.

The panels 30 employed in the above assembly may each have the fins 58, 62, and 64 previously installed. Alternatively, the installation of the fins may be performed after the assembly of the panels 30. It will be evident that the alignment of the elongate apertures illustrated yields a plurality of continuous apertures through the assembly of plates. Appropriate secondary fin stock may be inserted through each of these continuous apertures in the form of a single long continuous strip of material such as 58, 62, or 64 of FIGURE 1. While not shown, it will be seen that such fin stock may be inserted :as from the upper portion of the assembly continuously downward to the lower end thereof, and then brazed to the tubes. This construction materially increases the amount of secondary heat exchange area available, as well as materially simplifying the additionof the fins.

It is also possible to position the panels 30 in the position shown in FIGURE 9 and hold them in place during insertion of the fin stock as indicated above. Following the brazing cf the fin stock to the tubes, the various panels 30 will be secured in the relationship shown without need for the spacer tubes 70 or fittings T1 and 72.

It will be apparent from the foregoing description and accompanying drawings that there has been provided a method of fabricating a heat exchange devicewhich is believed to provide a solution to the foregoing problems and achieve the aforementioned objects. It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to' be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts, and detail of operation, but rather is intended to encompass all such modifications as are within the spirit and scope of the invention .as set forth in the appended claim.

What I claim and desire to secure by Letters Patent is:

A method of fabricating a heat exchange device from a plurality of composite sheets each formed of two superposed planar sheets having a pattern of weld-preventing material interposed between said sheets, said pattern including a pair of parallel spaced-apart bands located adjacent opposite edges of said composite sheet and extending to a transverse edge of said sheet and a plurality of closely spaced-apart bands lying parallel to said transverse edge and joined at opposite ends with said pair of bands, said pair of bands and plurality of bands thereby defining islands free of said weld-preventing material, said method comprising the steps of (A) slitting each said composite sheet in said weld preventing material free islands over a major portion of the length thereof to provide a plurality of individual first strips of said composite sheet,

(B) slitting each said composite sheet in a peripheral margin area thereof parallel to said weld-preventing material free islands to provide at least one second strip of said composite sheet, said second strip being devoid of weld-preventing material,

(C) twisting said first and second strips out of the normal plane of said composite sheet over a major portion of the length of said first and second strips to dispose said first and second strips in parallel spacedapart relationship lying in. planes substantially at right angles to said plane of said composite sheet, thereby forming elongate apertures between adajcent confronting surfaces of said first and second strips,

(D) forming a system 'of internal passageways within each said composite sheet corresponding to said pattern of weld-preventing material by applying thereto a fluid under pressure to expand the areas of said composite sheet covered with said weld-preventing material,

(E) joining said composite sheets in superposed,

spaced-apart relationship with the elongate apertures of each said composite sheet in aligned relationship,

(F) inserting a continuous strip of fin stock in the aligned elongate apertures of the superposed, spacedapart composite sheets, and

(G) securing said fin stock to said confronting surfaces of said first and second strips.

References Cited by the Examiner FOREIGN PATENTS 1,238,450 7/ 1960 France.

JOHN F. CAMPBELL, Primary Examiner.

J. D. HOBART, Assistant Examiner. 

